Furnace construction



Patented Dec. 3, 1946 FURNACE CONSTRUCTION Charles W. Nichols, West Orange, N. L, assignor to Charles W. Nichols, In, New York, N. Y.

Application Marchli, 1944, Serial No. 525,153

- terials such as above referred to. In its preferred form the furnace includes a plurality of superposed zones with means within the top of the upper zone for feeding and projecting the material in directions to impinge upon the side walls around within this zone, whereby the material may then fall on to an annular ledge and thence through a central opening into the next zone, onto a pile of the material supported on a stationary hearth. During its fall, the material comes in contact with a countercurrent flow of hot gases. The material may then roll down along the sides of such pile through peripheral discharge ports in the stationary hearth, and thence into van additional lower zone or zones where it may be rabbled in the form of relatively thin layers, over one or more hearths while being further roasted and finally cooled. If desired, instead of using but two upper zones through which the material falls, three, four or more of such zones may be provided, alternate zones having central and peripheral discharge ports or openings. I v

Various further objects, features and advantages of the invention will appear from the de scription given below taken in connection with the accompanying drawing which illustrates by way of example preferred forms of furnace structures involving the invention. The invention consists in such novel methods and combinations of method steps as are disclosed herein and also such novel features and combinations of parts as may be shown and described in connection with the furnace apparatus herein disclosed.

In the drawing:

Fig. 1 is a vertical sectional view of a furnace embodying the invention in one of its preferred forms; and

Fig. 2 is a similar view showing upper and lower portions of another form of furnaceembodying the invention.

The furnace as shown in Fig. 1 may comprise an outer cylindrical wall ID of suitable brick con- 4 Claims. (Cl. 263-21) struction with fire brick lining if desired. Within this wall a plurality of superposed chambers 0r zones may be provided as at ll, l2, l3 and I4. A suitable feeding device as at l5 may be mount- .ed to protrude down through the mid portion of the roof l6 of the furnace. This feeding device may include a hopper ll with a cylindrical outlet l8 extending down into the middle of the upper part of zone II. A vertically extending-rotatable shaft l9 may be mounted in suitable bearings as shown within the feed outlet Hi, this shaft carrying at its lower end a rotatable disc-like feeding device 20 having on its upper surfaces plurality of generally radially extending ribs 'or vanes as at 2| for causing the material as fed, to be projected outwardly as at 22 in a direction to impinge upon the inside walls as at 23 of the chamber l I. The shaft l9 may be driven as from a motor 24 connected through suitable transmission means as at 25.

The lower portion of zone or chamber ll may be demarked by a generally annular stepped ledge formation 26 formed of the brick work, protruding inwardly from the furnace walls and surrounding a central opening 21 which connects zone II with the next lower zone l2. It will be noted that the material as it falls in zone H is distributed in a generally globular and substantially hollow formation, the lower annular portion of which comprises the upper side of the ledge formation 26. In a manner hereinafter explained, provision is made for a, countercurrent stream of hot gas to flow up through opening 21, thence up through said globular formation and out through the roof by way of gas discharge conduits as at 28.

The upper side of the stepped ledge formation 26 may be made such that masses of the material will accumulate thereon until the natural angle of repose of the particular material being treated is reached. Thereupon further material which falls on this ledge will roll or slide down over the surface of the accumulations, to fall through the opening 2'! at its periphery and thereby cause a falling stream of generally cylindrical cross section in the chamber l2. At the side walls of this chamber a plurality of oil burners or other combustion apparatus as at 28 may be arranged to project flames into the falling stream of particles, and the resulting gaseous products of combustion will pass countercurrent with the material through opening 2! into and up through chamber II as above described.

The bottom of chamber I! may comprise a stationary hearth as at 20 having a plurality of 3 peripheral discharge ports as at 30. The material as it falls on this hearth will form a generally conical pile as at 29' and when the sides of .this pile reach the angle corresponding to the natural angle of repose of the material being treated, then subsequent falling material will roll or slide down along the sides of the pile for discharge through the ports 30. From these ports the material may fall onto a lower stationary hearth as at 3i, over which it may be agitated, rabbled and stirred while being advanced toward a central discharge port as at 32. The agitating may be accomplished by rotary rabbling structure such as used in furnaces well known under the trade name Herreshofl."

This abbling structure may for example comrise a central rotatable shaft as at 33 mounted atits lower end within suitable bearings contained within housing structures shown at 34, 35, and adapted to be rotated as by gears'36. Rabble arms as at 31 may extend from the central shaft out over the hearth 3| at various angular positions for carrying rabble teeth as at 38.

Theseteeth may be arranged in accordance with known practice'at' angles such that the layer of material onthe hearth is periodically agitated and advanced inwardly of the hearth toward the discharge port 32. I

If the furnace includes a further chamber as at H, a bottom hearth as at 40 may be provided and accompanied by similar rabble arms with teeth as at 31', the teeth here being arranged at angles to advance the material outwardly of hearth 40 to a discharge port 4| connected to 42 positioned beneath the furnace.

The rabbling structure may be internally cooled in accordance with known practice by streams of cooling air admitted for example to the base of the shaft as through a conduit 43. If desired, 40

a part of the cooling air may be discharged onto the material on hearth 40 through rabble arm openings as at 44. These openings may be constructed for example in accordance with those disclosed in patent to Connolly, No. 2,302,841, granted November 24, 1942. Further amounts of the cooling air if desired may be discharged through openings as at 44 formed directly in the central shaft 33 preferably at a point just be neath the hearth discharge port 32.

If desired, additional oil burners may be provided as at 35 to direct flames into the chamber l3. The gaseous products of combustion in chamber i3 may be allowed to pass up through ports 30 in hearth'23 to provide all or a part of 55 the heat in the upper zones.

In addition to the air introduced in chamber ll through rabble arm openings 44, further cooling air if desired may be introduced as through an inlet 43 having an adjustable damper as 50 shown, and connected to inletports as at 43 positioned around the walls of chamber ll,

In the form of construction shown in Fig. 2. the upper chamber li' may have a top wall as'at 30 formed with a plurality of peripheral gas discharge ports as at ll, opening into a'chamber 32 within the top of the furnace and from which the gases may be withdrawn throughan outlet 53. Clean-outdoors for the chamber 32 may be provided as indicated at 34. This arrangement of 70 the gas cutlets may be provided to insure a more uniform discharge of the gas from various points around the periphery of the upper portion of the chamber H.

In the construction shown in Fig. 2, if desired the ore feeding disc 20' may be stationary and the feed or inlet pipe 55 may be connected with a device such as a blower 58 whereby the material to be treated is carried into the furnace by air or gas injection instead; of by the mechanical feeding means of Fi 1.

In the lower portion of the furnace, as shown in the embodiment of Fig. 2, the zone 13 is constructed without the rabbling structure present 10 in Fig. 1. Instead, the material dropping through ports 30', falls down along the furnace walls through flames from burners as at 45,,onto an inverted conical ledge 60 forming a part of the bottom of the furnace. On the ledge 63 some of the material may accumulate until its natural angle of repose is reached, whereupon further material will slide and roll down and out the discharge port 6 I. If desired, any suitable known means may be provided at the discharge outlet 20 8! to regulate the flow .therethrough.

The arrangement as provided in the upper chambers or zones as at H or II is particularly advantageous for a number of reasons. The location and'arrangement of the feeding device is such that as the material is introduced into the furnace, it is forcefully distributed first outwardly in somewhat tangential and radial directions, generally horizontally and somewhat downwardly through the uprising streams of gas for uniform initial heating. As the particles strike the furnace walls in the upper zone, any lumps of substantial size will bebroken up and the particles will be deflected to some extent out into the uprising gas as they falldown to the ledge any suitable known type of cooling device s at 5 structure 28. The generally globular formation.

45 inwardly 50 that as some fall through the opening 21, intimate contact with the constricted rising gas stream is insured and the rising a stream in this restricted opening retards the fall of the particles to some extent.

The cylindrical formation which the distributed falling particles assumein chamber I2 is well adapted to insure many possibilities of contact with the hot gases coming from the sides of this chamber as such gases on their way up to the opening 21, pass through the cylindrical formation of particles. Furthermore, the particles as they fall from around the periphery of opening 21, are well distributed as they fall on the central part of the conical pile 23, so that nonuniform feeding -or clogging at the ports "is avoided. Provision of a conical pile of the material on hearth 28 provides a surface over'which the. particles can again roll or. slide down with retarded motion in the presence of the hot gases,

5:, to the discharge ports 33. Since the natural angle of repose of the material of pile 23' will automatically vary. depending upon the fineness and character of the material, generally unifonn feeding by gravity from the sides of such pile is made possible without the necessity of any moving parts in this zone. Furthermore, if some of the materialas it falls on the pile should still be in a moist or somewhat sticky condition, such parts of the material will remain on this pile for 7s a longer period for further heat treatment and will not tend to roll or slide of! through the ports as rapidly as the material which is dry and finely divided and needs no further treatment in this zone.

Ample provision is thus made for fairly prolonged and selective treatmentof the particles in zones II and I2, without the necessity of any moving parts in either of these chambers, except for the feed device if desired.

The lower hearth or hearths with the rabbling means may if desired be used either as cooling hearths, or one Or more of such hearths may be used for further roasting, in case the material is such that it should be subjected to more prolonged heat treatment with agitation,

While the invention has been described in detail with respect to particular preferred examples, it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be se-. cured by Letters Patent is:

1. A furnace construction for treating freeflowing masses of finely divided material, comprising a chamber having a plurality of superposed heating zones, means for feeding and projecting the material from the upper mid portion of the upper zone in directions to impinge on the prising a chamber having a plurality 01' super posed heating zones, rotary means for feeding side walls around within the upper zone, a ledge 7 charge ports.

2. A furnace construction for treating i'reeflowing masses of finely divided material, comportion 01 the upper zone in directions to impinge on the side walls around within the upper zone, a ledge protruding inwardly from said side walls to separate said upper zone from the next lower zone and surrounding acentral opening connecting such zones, a hearth forming the bottom of said next lower zone, said hearth being formed with peripheral discharge ports therethrough, whereby the material may fall from said side walls in the upper zone onto said ledge, thence through said central opening to form a pile atthe' middle portion of said hearth, and

' from which pile, material may flow through said ing the latter hearth to form a chamber, means for maintaining a heated atmosphere in such chamber, and means for dropping continuous supplies of distributed particles of the material into the chamber and onto the latter hearth to form a substantially conical pile, whereby further falling material rolls and slides. down the sides of such pile. and through said ports.

4. Method for roasting finely divided material which comprises causing same to fall through a stream of hot gas, onto a generally conical pile of the material supported on a stationary hearth in a closed chamber and in the presence of a heated atmosphere, allowing the material to then roll and slide down along the sides of such pile and fall from the periphery thereof onto a lower hearth, and then stirring and advancing the material as a relatively thin layer over the latter hearth.

CHARLES W. NICHOLS. 

